Onboard battery

ABSTRACT

An onboard battery includes battery modules each containing battery cells, a housing case that houses the battery modules, and an air intake duct configured to send cooling air into the modules. Of the battery modules, at least two are disposed apart from each other in a vertical direction and at least two are disposed apart from each other in a front-rear direction. Cooling air is taken into the battery modules from rear via the air intake duct. Cooling air taken into the battery modules is emitted to an internal space of the housing case. A rear portion of the housing case is provided with an exhaust hole configured to let out cooling air emitted from the battery modules to the internal space. Of emission flows of cooling air emitted from the battery modules, the emission flow of cooling air from at least one of the modules disposed most forward is the largest.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application claims priority from Japanese Patent ApplicationNo. 2018-057695 filed on Mar. 26, 2018, the entire contents of which arehereby incorporated by reference.

BACKGROUND 1. Technical Field

The present invention relates to a technical field regarding an onboardbattery that is to be mounted on a vehicle such as an automobile.

2. Related Art

Various vehicles, such as automobiles, are provided with vehicularbatteries for supplying electric power to electric motors and variousother electrical component parts

In recent years, in particular, vehicles that use electric power asmotive power, such as electric vehicles (EVs) and hybrid electricvehicles (HEVs), are becoming widely used. These fully or partlyelectrically powered vehicles are provided with vehicular batteries thathave high electricity storage function.

An onboard battery is made up of a housing case and a battery modulehoused in the housing case. A battery module contains, for example, anarrangement of battery cells (secondary batteries), such as nickel metalhydride batteries or lithium ion batteries. Furthermore, in vehicularbatteries that are mounted in electric vehicles and the like, aplurality of battery modules are disposed in a housing case and theindividual battery cells of the battery modules are coupled in series orparallel.

Some of such vehicular batteries have an arrangement for securing highelectricity storage function in which battery modules are disposed in apair of upper and lower tiers in the housing case (see, e.g., JapanesePatent No. 5206110).

An onboard battery described in Japanese Patent No. 5206110 is disposedin a luggage compartment in a rear portion of a vehicle in such a mannerthat the lower-tier battery module is inserted in a recess portion thatis formed in a floor panel and that has an upper opening. Thisconfiguration secures a large space for the luggage compartment.

SUMMARY OF THE INVENTION

An aspect of the invention provides an onboard battery including:battery modules in each of which a battery cell is disposed; a housingcase that houses the battery modules; and an air intake duct configuredto send cooling air into the battery modules. Of the battery modules, atleast two are disposed apart from each other in a vertical direction andat least two are disposed apart from each other in a front-reardirection. Cooling air is taken into the battery modules from rear viathe air intake duct. Cooling air taken into the battery modules isemitted to an internal space of the housing case. A rear portion of thehousing case is provided with at least one exhaust hole for letting outthe cooling air emitted from the battery modules to the internal spaceof the housing case. Of emission flows of the cooling air emitted fromthe battery modules to the internal space of the housing case, theemission flow of the cooling air emitted from at least one of thebattery modules which is disposed at the most forward location is thelargest.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an example of an onboard battery,illustrating, together with FIGS. 2 to 12, an onboard battery accordingto the invention;

FIG. 2 is a perspective view of an onboard battery from which portionsof the battery have been omitted;

FIG. 3 is a schematic diagram illustrating, for example, how batterymodules of an onboard battery are arranged;

FIG. 4 is a schematic exploded perspective view of a battery module anda joint duct;

FIG. 5 is a perspective view of a first cooling unit;

FIG. 6 is a perspective view of a second cooling unit;

FIG. 7 is a perspective view of a first battery module and a first jointduct, illustrating, together with FIGS. 8 to 11, a battery module and ajoint duct;

FIG. 8 is a perspective view of a second battery module and a secondjoint duct;

FIG. 9 is a perspective view of a third battery module and a third jointduct.

FIG. 10 is a perspective view of a fourth battery module and a fourthjoint duct;

FIG. 11 is a perspective view of a fifth battery module and a fifthjoint duct; and

FIG. 12 is a conceptual diagram illustrating an example of an onboardbattery in which two battery modules are disposed at a most forwardlocation.

DETAILED DESCRIPTION

In the following, some preferred examples of the present invention aredescribed in detail with reference to the accompanying drawings. Notethat the following description is directed to illustrative instances ofthe disclosure and not to be construed as limiting to the presentinvention. Factors including, without limitation, numerical values,dimensions, shapes, materials, components, positions of the components,and how the components are coupled to each other are for purposes ofillustration to give an easier understanding of the present invention,and are not to be construed as limiting to the present invention, unlessotherwise specified. Further, elements in the following instances whichare not recited in a most-generic independent claim of the disclosureare optional and may be provided on an as-needed basis. The drawings areschematic and are not intended to be drawn to scale. Throughout thespecification and the drawings, elements having substantially the samefunction and configuration are denoted with the same minerals to avoidredundant description. Illustration of elements that are not directlyrelated to the present invention is omitted. In an onboard batterymounted in a vehicle, since the battery cells produce heat at the timeof driving the vehicle, the battery cells need to be cooled to reduce orinhibit the temperature increase caused by the heat production of thebattery cells so as to secure good performance of the battery cells andvarious control devices disposed within the housing case. However, whena complicated exhaust path is provided within the housing case, smoothexhaustion may become difficult to secure, leading to a possibility offailing to secure sufficient cooling performance.

Particularly in an onboard battery made up of a plurality of batterymodules as described above, a large quantity of heat is produced, makingit more desirable to secure smooth exhaustion and therefore improve theefficiency in cooling the battery modules.

Therefore, it is desirable to provide an onboard battery that securessmooth emission of cooling air and therefore improves the efficiency incooling the battery cells.

An onboard battery 1 includes a housing case 2 and battery modules 3, 3,. . . (see FIGS. 1 to 3). The onboard battery 1 is disposed, forexample, in a luggage compartment (or trunk) of a vehicle.

The housing case 2 has a housing portion 4 that has an upper opening anda flat platy lid 5 that closes the opening of the housing portion 4 fromabove.

The housing portion 4 has a front portion 6 disposed in rear of a rearseat of the vehicle, a rear portion 7 disposed in rear of the frontportion 6, side portions 8 and 8 disposed apart from each other in aright-left or lateral direction, and a bottom portion 9 that faces in avertical direction.

As illustrated in FIG. 3, an intermediate portion of the front portion 6in the vertical direction is provided as a flat portion 6 a that facesin a front-rear direction, a portion of the front portion 6 above theflat portion 6 a is provided as an upper inclined portion 6 b that isinclined so as to extend farther rearward with increasing distanceupward from the flat portion 6 a, and a portion thereof below the flatportion 6 a is provided as a lower inclined portion 6 c that is inclinedso as to extend farther rearward with increasing distance downward fromthe flat portion 6 a.

A lower end of the upper inclined portion 6 b is continuous with anupper end of the flat portion 6 a and an upper end of the lower inclinedportion 6 c is continuous with a lower end of the flat portion 6 a. Theupper inclined portion 6 b has, for example, a curved shape that iscurved to be convex or protruded diagonally forward and upward and thelower inclined portion 6 c has, for example, a curved surface that iscurved to be convex or protruded diagonally rearward and upward.

The rear portion 7 has exhaust holes 7 a and 7 a, and exhaust holes 7 b,7 b, and 7 b (see FIGS. 1 to 3). The exhaust holes 7 a and 7 a areprovided at an upper end side of the rear portion 7 and apart from eachother in the right-left direction and the exhaust holes 7 b, 7 b, and 7b are provided at a lower end side of the rear portion 7 and apart fromone another in the right-left direction.

As for the battery modules 3, 3, . . . , for example, five batterymodules are disposed in an arrangement in the front-rear and verticaldirections within the housing case 2. Specifically, the five batterymodules 3, 3, . . . in this example are a first battery module 3Apositioned most forward, a second battery module 3B positioned at a rearside of the first battery module 3A, a third battery module 3Cpositioned at the rear side of the second battery module 3B, a fourthbattery module 3D positioned at the rear side of the first batterymodule 3A and directly above the second battery module 3B, and a fifthbattery module 3E positioned at the rear side of the fourth batterymodule 3D and directly above the third battery module 3C.

The first battery module 3A, the second battery module 3B, the thirdbattery module 3C, the fourth battery module 3D, and the fifth batterymodule 3E are coupled in series by electric wires.

Each battery module 3 includes a case body 10 and a plurality of batterycells 11, 11, . . . housed within the case body 10 (see FIG. 4).

The case body 10 has a laterally elongated box shape that is open upwardand rearward and that is defined by a laterally elongated front surfaceportion 12 that faces in the front-rear direction, side surface portions13 and 13 that face in the right-left direction and are apart from eachother in the right-left direction, and a laterally elongated bottomsurface portion 14 that faces in the vertical direction. An internalspace of the case body 10 is formed as a housing space 10 a.

The front surface portion 12 has in one of a right end portion, a leftend portion, and a central portion in the right-left direction a releasehole 12 a that penetrates the front surface portion 12 in the front-reardirection. Concretely, the first battery module 3A has a release hole 12a formed, for example, in a right end portion of its front surfaceportion 12, the second battery module 3B has a release hole 12 a formed,for example, in a left end portion of its front surface portion 12, thethird battery module 3C has a release hole 12 a formed, for example, ina central portion of its front surface portion 12 in the right-leftdirection, a fourth battery module 3D has a release hole 12 a formed,for example, in a right end portion of its front surface portion 12, anda fifth battery module 3E has a release hole 12 a formed, for example,in a central portion of its front surface portion 12 in the right-leftdirection. FIG. 4 illustrates an example in which a release hole 12 a isformed in a right end portion of the front surface portion 12.

The battery cells 11, 11, . . . are housed within the housing space 10a, for example, in a state in which the battery cells 11, 11, . . . arealigned at equal intervals in the right-left direction in such anorientation that the direction of thickness of the battery cells 11, 11,. . . coincides with the right-left direction, and are thus supported inthe case body 10. When the battery cells 11, 11, . . . are supported inthe case body 10, the battery cells 11, 11, . . . are spaced from eachother by constant clearances. The battery cells 11, 11, . . . arecoupled in series.

A cover 15 having a laterally elongated shape is attached to the casebody 10. The cover 15 includes a base plate member 15 a that faces inthe vertical direction and a tube-shaped portion 15 b that is positionedon an upper surface of the base plate member 15 a. The tube-shapedportion 15 b is positioned at a central portion of the base plate member15 a in the front-rear direction. The cover 15 is attached to the casebody 10 in such a manner that the base plate member 15 a closes theupper opening of the case body 10.

The central portion of the cover 15 in the front-rear direction isprovided with penetrating gas flow holes (not illustrated) that eachextend in the vertical direction and that are aligned at equal intervalsin the right-left direction. The gas flow holes of the cover 15 are eachpositioned directly over the battery cells 11, 11, . . . .

As for the cover 15, a pair of front and rear sides of the tube-shapedportion 15 b are provided with substrates 16 and 16 that each have alaterally elongated shape. Electric wires are coupled to the substrates16 and 16, so that, using electric wires and the substrates 16 and 16,electrical control or the like is performed on the battery cells 11, 11,. . . .

Each of the battery cells 11, 11, . . . is provided with a valve (notillustrated) capable of communication with an interior of the batterycell 11. Each valve communicates with a corresponding one of the gasflow holes of the cover 15. If abnormality should occur in a batterycell 11, gas may sometime be produced inside the battery cell 11. Theproduction of gas will increase the internal pressure in the batterycell 11, so that the valve becomes open, allowing produced gas to flowout via the valve and the gas flow hole into the tube-shaped portion 15b.

The battery modules 3, 3, . . . are each mounted in the housing case 2via a mounting plate (not illustrated) and disposed at predeterminedposition (see FIG. 3). The second battery module 3B and the thirdbattery module 3C are disposed in a lower tier, the fourth batterymodule 3D and the fifth battery module 3E are disposed in an upper tier,and the first battery module 3A is disposed in an intermediate tierrelative to the second battery module 3B and the third battery module 3Cin the lower tier and to the fourth battery module 3D and the fifthbattery module 3E in the upper tier. It is to be noted that the firstbattery module 3A may be disposed in the same lower tier as the secondbattery module 3B and the third battery module 3C or may also bedisposed in the same upper tier as the fourth battery module 3D and thefifth battery module 3E.

When the battery modules 3, 3, . . . are driven, cooling air is takeninto the battery modules 3, 3, . . . by a first air intake unit 17 andby a second air intake unit 18 (see FIGS. 1, 3, 5, and 6).

The first air intake unit 17 includes a first air intake duct 19, afirst air intake fan 20, a first intake pipe 21, and joint ducts 22, 22,and 22 (see FIGS. 1 and 5).

The first air intake duct 19 has a function of sending cooling air intothe first battery module 3A, the second battery module 3B, and the thirdbattery module 3C. The first air intake duct 19 includes an intakeportion 23, an intermediate portion 24, a first inflow portion 25, asecond inflow portion 26, and a third inflow portion 27.

The intake portion 23 is continuous with the intermediate portion 24.The intake portion 23 is located at a higher or upper side of, that is,higher than, the intermediate portion 24. The intermediate portion 24 ispositioned in a substantially horizontal posture at the rear side of alower half of the housing case 2.

As for the first inflow portion 25, a portion other than a front endportion extends in the front-rear direction and the front end portion isbent upward relative to the other portion. A rear end portion of thefirst inflow portion 25 is continuous with a left end portion of theintermediate portion 24. A portion of the second inflow portion 26 otherthan a front end portion of the second inflow portion 26 extends in thefront-rear direction and the front end portion is bent upward relativeto the other portion. A rear end portion of the second inflow portion 26is continuous with a right end portion of the intermediate portion 24.The third inflow portion 27 extends in the front-rear direction. A rearend portion of the third inflow portion 27 is continuous with asubstantially central portion of the intermediate portion 24 in theright-left direction. The first inflow portion 25, the second inflowportion 26, and the third inflow portion 27 are configured so that theirlengths in the front-rear direction are progressively shorter in thatorder.

The first air intake fan 20 is coupled to an upper end portion of theintake portion 23.

A lower end portion of the first intake pipe 21 is coupled to the firstair intake fan 20. Therefore, when the first air intake fan 20 isrotated, cooling air is taken in through the first intake pipe 21 andthe taken-in cooling air is forced to flow toward the first air intakeduct 19.

The joint ducts 22, 22, and 22 provided for the first air intake duct 19in this example are a first joint duct 22A, a second joint duct 22B, anda third joint duct 22C. The first joint duct 22A has a function ofsending cooling air into the first battery module 3A, the second jointduct 22B has a function of sending cooling air into the second batterymodule 3B, and the third joint duct 22C has a function of sendingcooling air into the third battery module 3C. The first joint duct 22A,the second joint duct 22B, and the third joint duct 22C are positionedin that order from front to rear.

The joint duct 22 includes a laterally elongated substantiallyrectangular coupling portion 28 and a connecting portion 29 protrudingfrom the coupling portion 28. The joint duct 22 has therein a space. Thecoupling portion 28 is provided with protrusions 28 a, 28 a, . . . forair ejection that are protruded forward and spaced from each other atequal intervals in the right-left direction. Each protrusion 28 a forair ejection has an open distal end.

A rear surface of the coupling portion 28 is a curved surface 28 b whoseintermediate portion in the vertical direction is protruded rearward.

The connecting portion 29 of the first joint duct 22A is protrudeddownward from a left end portion of the coupling portion 28 and coupledto the front end portion of the first inflow portion 25. The connectingportion 29 of the second joint duct 22B is protruded downward from aright end portion of the coupling portion 28 and coupled to the frontend portion of the second inflow portion 26. The connecting portion 29of the third joint duct 22C is protruded rearward from a central portionof the coupling portion 28 in the right-left direction and coupled tothe front end portion of the third inflow portion 27.

The second air intake unit 18 includes a second air intake duct 30, asecond air intake fan 31, a second intake pipe 32, and joint ducts 22,22 (see FIGS. 1 and 6).

The second air intake duct 30 has a function of sending cooling air intothe fourth battery module 3D and the fifth battery module 3E. The secondair intake duct 30 includes an intake portion 33, an intermediateportion 34, a fourth inflow portion 35, and a fifth inflow portion 36.

The intake portion 33 is continuous with the intermediate portion 34.The intake portion 33 is located above, that is, at the upper side of,the intermediate portion 34. The intermediate portion 34 is positionedin a substantially horizontal posture at the rear side of an upper halfof the housing case 2.

The intermediate portion 34 of the second air intake unit 18 is locatedat the upper side of the intermediate portion 24 of the first air intakeunit 17. Therefore, the intermediate portion 24 and the intermediateportion 34 do not overlap each other when viewed in the front-reardirection, so that the onboard battery 1 can be reduced in size in thefront-rear direction.

A portion of the fourth inflow portion 35 other than a front end portionof the fourth inflow portion 35 extends in the front-rear direction andthe front end portion is bent rightward relative to the other portion. Arear end portion of the fourth inflow portion 35 is continuous with aleft end portion of the intermediate portion 34. The fifth inflowportion 36 extends in the front-rear direction and a rear end portionthereof is continuous with a right end portion of the intermediateportion 34. The fourth inflow portion 35 is longer in the front-reardirection than the fifth inflow portion 36.

The second air intake fan 31 is coupled to an upper end portion of theintake portion 33.

A lower end portion of the second intake pipe 32 is coupled to thesecond air intake fan 31. Therefore, when the second air intake fan 31is rotated, cooling air is taken in through the second intake pipe 32and the taken-in cooling air is forced to flow toward the second airintake duct 30.

The joint ducts 22 and 22 provided for the second air intake duct 30 inthis example are a fourth joint duct 22D and a fifth joint duct 22E. Thefourth joint duct 22D has a function of sending cooling air into thefourth battery module 3D and the fifth joint duct 22E has a function ofsending cooling air into the fifth battery module 3E. The fourth jointduct 22D is positioned more forward than the fifth joint duct 22E.

The connecting portion 29 of the fourth joint duct 22D is protrudedleftward from a left end portion of the coupling portion 28 and coupledto the front end portion of the fourth inflow portion 35. The connectingportion 29 of the fifth joint duct 22E is protruded rearward from acentral portion of the coupling portion 28 in the right-left directionand coupled to the front end portion of the fifth inflow portion 36.

For example, of the first inflow portion 25, the second inflow portion26, the third inflow portion 27, the fourth inflow portion 35, and thefifth inflow portion 36 of the onboard battery 1, the first inflowportion 25 is provided with the largest inside diameter. Therefore, ofthe first inflow portion 25, the second inflow portion 26, the thirdinflow portion 27, the fourth inflow portion 35, and the fifth inflowportion 36, the first inflow portion 25 carries the largest flow ofcooling air.

As for the first air intake unit 17, the first inflow portion 25, thesecond inflow portion 26, and the third inflow portion 27 are insertedfrom rear into the exhaust holes 7 b, 7 b, and 7 b formed in the housingcase 2. When the first inflow portion 25, the second inflow portion 26,and the third inflow portion 27 have been inserted in exhaust holes 7 b,7 b, and 7 b, a certain clearance gap is formed between an outerperipheral surface of each of the first inflow portion 25, the secondinflow portion 26, and the third inflow portion 27 and an opening edgeof a corresponding one of the exhaust holes 7 b, 7 b, and 7 b. Theseclearance gaps allow air inside the housing case 2 to flow out of thehousing case 2.

The coupling portion 28 of the first joint duct 22A is coupled to a rearend portion of the case body 10 of the first battery module 3A (see FIG.7) and therefore positioned to face rear surfaces of the battery cells11, 11, . . . . The first inflow portion 25 coupled to the first batterymodule 3A is positioned below the second battery module 3B and the thirdbattery module 3C within the housing case 2.

The coupling portion 28 of the second joint duct 22B is coupled to arear end portion of the case body 10 of the second battery module 3B(see FIG. 8) and therefore positioned to face rear surfaces of thebattery cells 11, 11, . . . . The second inflow portion 26 coupled tothe second battery module 3B is positioned below the third batterymodule 3C within the housing case 2.

The coupling portion 28 of the third joint duct 22C is coupled to a rearend portion of the case body 10 of the third battery module 3C (see FIG.9) and therefore positioned to face rear surfaces of the battery cells11, 11, . . . .

The coupling portion 28 of the fourth joint duct 22D is coupled to arear end portion of the case body 10 of the fourth battery module 3D(see FIG. 10) and therefore positioned to face rear surfaces of thebattery cells 11, 11, . . . . The fourth inflow portion 35 coupled tothe fourth battery module 3D is positioned at the left side of the fifthbattery module 3E within the housing case 2.

The coupling portion 28 of the fifth joint duct 22E is coupled to a rearend portion of the case body 10 of the fifth battery module 3E (see FIG.11) and therefore positioned to face rear surfaces of the battery cells11, 11, . . . .

As described above, the coupling portions 28, 28, . . . of the jointducts 22, 22, . . . are each positioned to face the rear surfaces of thebattery cells 11, 11, . . . of a corresponding one of the batterymodules 3, 3, . . . . At this time, the protrusions 28 a, 28 a, . . .for air ejection of each coupling portion 28 are positioned between thebattery cells 11, . . . . Therefore, cooling air ejected from theprotrusions 28 a, 28 a, . . . for air ejection flows forward throughgaps between the battery cells 11, 11, . . . .

Flow paths of cooling air will be described below.

When the first air intake fan 20 and the second air intake fan 31 arerotated, air present outside the housing case 2 is taken as cooling airvia the first intake pipe 21 and the second intake pipe 32 into thefirst air intake duct 19 and the second air intake duct 30.

Cooling air taken into the first air intake duct 19 then flows from theintake portion 23 into the intermediate portion 24 and branches into thefirst inflow portion 25, the second inflow portion 26, and the thirdinflow portion 27. Branched cooling air is forced to flow toward thefirst joint duct 22A, the second joint duct 22B, and the third jointduct 22C and ejected into the first battery module 3A, the secondbattery module 3B, and the third battery module 3C.

Cooling air ejected into the first battery module 3A, the second batterymodule 3B, and the third battery module 3C flows forward passing throughgaps formed between the battery cells 11, 11, . . . . Thus, cooling aircools the battery cells 11, 11, . . . . After flowing forward throughthe gaps between the battery cells 11, 11, . . . , cooling air isemitted into the internal space of the housing case 2 through releaseholes 12 a, 12 a, and 12 a of the front surface portions 12, 12, and 12.

At this time, since the rear surface of the coupling portion 28 of thefirst joint duct 22A coupled to the first battery module 3A is thecurved surface 28 b whose intermediate portion in the vertical directionis protruded rearward, part (indicated by B1 in FIG. 3) of the coolingair emitted through the release hole 12 a of the second battery module3B is guided by the curved surface 28 b so as to easily flow upward andthen rearward.

Furthermore, the rear surface of the coupling portion 28 of the secondjoint duct 22B coupled to the second battery module 3B is the curvedsurface 28 b whose intermediate portion in the vertical direction isprotruded rearward, cooling air (indicated by C1 and C2 in FIG. 3)emitted from the release hole 12 a of the third battery module 3C isguided by the curved surface 28 b so as to easily flow upward ordownward and then rearward.

On the other hand, cooling air taken into the second air intake duct 30is forced to flow through the intake portion 33 into the intermediateportion 34 and then branched into the fourth inflow portion 35 and thefifth inflow portion 36. Branched cooling air flows toward the fourthjoint duct 22D and the fifth joint duct 22E and then is ejected into thefourth battery module 3D and the fifth battery module 3E.

Cooling air ejected into the fourth battery module 3D and the fifthbattery module 3E flows forward passing through gaps formed between thebattery cells 11, 11, . . . . Thus, cooling air cools the battery cells11, 11, After flowing forward through the gaps between the battery cells11, 11, . . . , cooling air is emitted into the internal space of thehousing case 2 from the release holes 12 a and 12 a of the front surfaceportions 12 and 12.

At this time, since the rear surface of the coupling portion 28 of thefirst joint duct 22A coupled to the first battery module 3A is thecurved surface 28 b whose intermediate portion in the vertical directionis protruded rearward, part (indicated by D2 in FIG. 3) of cooling airemitted from the release hole 12 a of the fourth battery module 3D isguided by the curved surface 28 b so as to easily flow downward and thenrearward.

Furthermore, since the rear surface of the coupling portion 28 of thefourth joint duct 22D coupled to the fourth battery module 3D is thecurved surface 28 b whose intermediate portion in the vertical directionis protruded rearward, cooling air (indicated by E1 and E2 in FIG. 3)emitted from the release hole 12 a of the fifth battery module 3E isguided by the curved surface 28 b so as to easily flow upward ordownward and then rearward.

Of the first battery module 3A, the second battery module 3B, the thirdbattery module 3C, the fourth battery module 3D, and the fifth batterymodule 3E in the onboard battery 1, the first battery module 3A disposedat the most forward location emits the largest flow of cooling air intothe internal space of the housing case 2.

Therefore, the cooling air emitted from the first battery module 3A tothe internal space of the housing case 2 forms major exhaust pathswithin the housing case 2 (see FIG. 3). Because, within the housing case2, a portion of the internal space other than both upper and lower endportions is provided with many component parts of the onboard battery 1,major exhaust paths are an upper side exhaust path F1 extending from afront side of the first battery module 3A through the upper side of thefourth battery module 3D and the fifth battery module 3E to the exhaustholes 7 a and 7 a formed in the rear portion 7 of the housing case 2 anda lower side exhaust path F2 extending from the front side of the firstbattery module 3A through the lower side of the second battery module 3Band the third battery module 3C to the exhaust holes 7 b, 7 b, and 7 bformed in the rear portion 7.

Cooling air A1 having flown through the upper side exhaust path F1 isemitted mainly from the exhaust holes 7 a and 7 a to the outside of thehousing case 2 while cooling air A2 having flown through the lower sideexhaust path F2 is emitted mainly from the exhaust holes 7 b, 7 b, and 7b to the outside of the housing case 2.

Thus, in the onboard battery 1, the cooling air emitted from the firstbattery module 3A, which emits the largest flow of air, forms the upperside exhaust path F1 and the lower side exhaust path F2, which are majorexhaust paths. Therefore, the cooling air emitted from each of thesecond battery module 3B, the third battery module 3C, the fourthbattery module 3D, and the fifth battery module 3E mainly joins the flowmoving through the upper side exhaust path F1 or the flow moving throughthe lower side exhaust path F2 and then flows out of the housing case 2.

That is, the cooling air D1 emitted from the fourth battery module 3Dand flowing upward joins the flow moving through the upper side exhaustpath F1 and then flows out of the housing case 2 and the cooling air E1emitted from the fifth battery module 3E and flowing upward joins theflow moving through the upper side exhaust path F1 and then flows out ofthe housing case 2. Furthermore, the cooling air B2 emitted from thesecond battery module 3B and flowing downward joins the flow movingthrough the lower side exhaust path F2 and then flows out of the housingcase 2 and the cooling air C2 emitted from the third battery module 3Cand flowing downward joins the flow moving through the lower sideexhaust path F2 and then flows out of the housing case 2.

Furthermore, each of the cooling air D2 emitted from the fourth batterymodule 3D and flowing downward, the cooling air E2 emitted from thefifth battery module 3E and flowing downward, the cooling air B1 emittedfrom the second battery module 3B and flowing upward, and the coolingair C1 emitted from the third battery module 3C and flowing upwardmainly flows through an intermediate portion of the internal space ofthe housing case 2 in the vertical direction and then flows out of thehousing case 2 through the exhaust holes 7 a, 7 a, 7 b, 7 b, and 7 b.

Note that part of the cooling air emitted into the internal space of thehousing case 2 from the first battery module 3A, the second batterymodule 3B, the third battery module 3C, the fourth battery module 3D,and the fifth battery module 3E flows through a right end portion or aleft end portion of the internal space of the housing case 2 and thenflows out of the housing case 2. However, the emission flow of coolingair that goes out of the housing case 2 after passing through the rightend portion or the left end portion of the internal space of the housingcase 2 is smaller than the emission flow of cooling air that goes out ofthe housing case 2 after passing through the upper side exhaust path F1,the lower side exhaust path F2, or the intermediate portion of theinternal space of the housing case 2 in the vertical direction.

A flue gas duct 37 is disposed to the left of the battery modules 3, 3,. . . (see FIG. 2). The flue gas duct 37 has branched portions that arecoupled to the tube-shaped portions 15 b, 15 b, . . . of the covers 15,15, . . . that cover the case bodies 10, 10, . . . of the batterymodules 3, 3, . . . . A distal end portion of the flue gas duct 37 isprovided with an exhaust portion 38 whose distal end opening is formedas an exhaust opening 38 a.

Gas produced at the time of abnormality occurring in any one of thebattery cells 11, 11, . . . is guided via a corresponding one of thetube-shaped portions 15 b, 15 b, . . . of the covers 15, 15, . . . tothe exhaust portion 38 of the flue gas duct 37 and is emitted out of thehousing case 2 through the exhaust opening 38 a.

In the internal space of the housing case 2, junction boxes 39 and 40that function as a control device that controls the battery modules 3,3, . . . are positioned side by side in the right-left direction at theupper side of the first battery module 3A and the front side of thefourth battery module 3D.

A region in the internal space of the housing case 2 in which thejunction boxes 39 and 40 are disposed is exposed to inflow of part ofthe cooling air that has been ejected from the joint ducts 22, 22, . . .and has cooled the battery cells 11, 11, . . . of the battery modules 3,3, . . . , so that such inflowing cooling air cools the junction boxes39 and 40.

In a right end portion of the internal space of the housing case 2 thereare disposed an auxiliary appliance 41 and a control unit (notillustrated) that are aligned in the vertical direction. The auxiliaryappliance 41 is an appliance for charging the onboard battery 1 when thevehicle is not running, for example, at night. The control unit controlsthe entire onboard battery 1.

Part of the cooling air having cooled the battery cells 11, 11, . . .flows into a region in the internal space of the housing case 2 in whichthe auxiliary appliance 41 is disposed and therefore cools the auxiliaryappliance 41 and the control unit.

As described above, in the onboard battery 1, at least two of thebattery modules 3, 3, . . . are disposed apart from each other in thevertical direction and at least two of the battery modules 3, 3, . . .are disposed apart from each other in the front-rear direction. The rearportion 7 of the housing case 2 is provided with the exhaust holes 7 a,7 a, 7 b, 7 b, and 7 b. Furthermore, the emission flows of cooling airemitted from the battery modules 3, 3, . . . to the internal space ofthe housing case 2 are set so that the emission flow from the firstbattery module 3A is the largest.

Therefore, a major exhaust path is formed in which cooling air taken infrom rear is emitted from the first battery module 3A to the internalspace of the housing case 2 at the largest emission flow of all the fivebattery modules 3A to 3E and, in the internal space of the housing case2, cooling air moves from the first battery module 3A toward the exhaustholes 7 a, 7 a, 7 b, 7 b, and 7 b. This makes it easier for cooling airemitted from the second battery module 3B, the third battery module 3C,the fourth battery module 3D, and the fifth battery module 3E to flowthrough the exhaust path extending from the first battery module 3Atoward the exhaust holes 7 a, 7 a, 7 b, 7 b, and 7 b and secures smoothemission of cooling air. Thus, the efficiency in cooling the batterycells 11, 11, . . . can be improved.

Furthermore, the first battery module 3A is disposed at the most forwardlocation, the fourth battery module 3D and the second battery module 3Bare disposed in the upper tier and the lower tier, respectively, at therear side of the first battery module 3A, and the first battery module3A is disposed in the intermediate tier in the vertical direction.

Therefore, since the emission flow of cooling air from the first batterymodule 3A disposed in the intermediate tier is set the largest, it iseasy for the cooling air emitted from the first battery module 3A tosplit into upper and lower flows, so that the cooling air smoothly flowsinside the housing case 2. Thus, the cooling air can be even moresmoothly emitted from the exhaust holes 7 a, 7 a, 7 b, 7 b, and 7 b.

The five battery modules 3, 3, . . . are disposed in such a manner thatthe fifth battery module 3E and the third battery module 3C are disposedin the upper tier and the lower tier, respectively, in rear of thefourth battery module 3D and the second battery module 3B that aredisposed in the upper tier and the lower tier, respectively.

Therefore, due to the arrangement in which battery modules 3, 3, . . .are disposed in the upper tier and the lower tier at an intermediatelocation and the most rearward location in the front-rear direction andone battery module 3 is disposed in the intermediate tier at the mostforward location, cooling air can be caused to smoothly flow inside thehousing case 2 and smoothly go out through the exhaust holes 7 a, 7 a, 7b, 7 b, and 7 b while generation of sufficient electric power isallowed.

Furthermore, of the plurality of exhaust holes 7 a, 7 a, 7 b, 7 b, and 7b provided, at least two exhaust holes are positioned apart from eachother in the vertical direction.

Therefore, the cooling air caused to flow through the upper side exhaustpath F1 inside the housing case 2 and the cooling air caused to flowthrough the lower side exhaust path F2 are emitted mainly through theupper exhaust holes 7 a and 7 a and the lower exhaust holes 7 b, 7 b,and 7 b, respectively, so that emission of cooling air out of thehousing case 2 can be smoothly carried out.

Furthermore, the front surface portions 12, 12, . . . of the batterymodules 3, 3, . . . are provided with release holes 12 a, 12 a, . . .for emitting cooling air into the internal space of the housing case 2.End portions of the first air intake duct 19 and the second air intakeduct 30 are provided as the coupling portions 28, 28, . . . that arecoupled to the rear end portions of the battery modules 3, 3, . . . andthe rear surfaces of the coupling portions 28, 28, . . . are formed asthe curved surfaces 28 b, 28 b, . . . whose intermediate portions in thevertical direction are protruded rearward.

Therefore, at least part of the cooling air emitted from the releaseholes 12 a, 12 a, . . . of the second battery module 3B, the thirdbattery module 3C, the fourth battery module 3D, and the fifth batterymodule 3E is easily guided by the curved surfaces 28 b, 28 b, . . . toflow upward or downward and then rearward, so that cooling air can bemore smoothly emitted through the exhaust holes 7 a, 7 a, 7 b, 7 b, and7 b.

Note that the curved surfaces 28 b and 28 b of the third battery module3C and the fifth battery module 3E also have a shape whose intermediateportion in the vertical direction is protruded rearward. Therefore, thecooling air passing through the upper side exhaust path F1, the lowerside exhaust path F2, and an intermediate portion of the internal spaceof the housing case 2 in the vertical direction is easily guided to flowupward or downward, by the curved surfaces 28 b and 28 b of the thirdbattery module 3C and the fifth battery module 3E, so that cooling aircan be smoothly emitted through the exhaust holes 7 a, 7 a, 7 b, 7 b,and 7 b.

In addition, the front end portion of the housing case 2 has atlocations above and below the first battery module 3A the upper inclinedportion 6 b and the lower inclined portion 6 c that become farther apartfrom each other in the vertical direction toward the rear, morespecifically, with increasing distance toward the rear.

Therefore, since the cooling air emitted from the first battery module3A is caused to flow rearward along the upper inclined portion 6 b andthe lower inclined portion 6 c, the cooling air caused to split into theupper and lower separate flows can be caused to smoothly flow rearwardwithin the housing case 2.

Note that, in the onboard battery 1, cooling air is taken into thebattery modules 3, 3, . . . from rear via the first air intake duct 19and the second air intake duct 30, and that the second battery module 3Band the fourth battery module 3D are disposed in the lower tier the andupper tier, the third battery module 3C and the fifth battery module 3Eare disposed in a pair of lower and upper tiers, and the first batterymodule 3A is disposed at the most forward location.

Therefore, the most forward location, where temperature is likely tobecome the highest, is provided with only the first battery module 3Ainstead of two or more battery modules, so that the effect of heatproduced by the other battery modules 3, 3, . . . on the first batterymodule 3A is reduced. Hence, the efficiency in cooling the batterymodules 3, 3, . . . can be improved and the temperature increase due toheat produced by the battery cells 11, 11, . . . can be reduced.

Furthermore, since the first battery module 3A disposed most forward isdisposed in the intermediate tier relative to the battery modules 3, 3disposed in the upper tier and the lower tier, the effect of heatproduced by the battery modules 3, 3, . . . positioned more rearwardthan the first battery module 3A on the first battery module 3A becomesfurther less, so that the temperature increase due to heat produced bythe battery cells 11, 11, . . . can be further reduced.

Although in the above-illustrated example, the five battery modules 3,3, . . . are disposed, it suffices that the number of battery modules 3disposed within the housing case 2 is at least three and that, of the atleast three battery modules 3, at least two battery modules 3, 3 aredisposed in a pair of upper and lower tiers and at least one batterymodule 3 is disposed at the most forward location.

For example, an arrangement in which two battery modules 3, 3 aredisposed in a pair of upper and lower tiers at the most forward locationmay be adopted (see FIG. 12). In this arrangement, of the emission flowsof cooling air emitted from the battery modules 3, 3, . . . to theinternal space of the housing case 2, the emission flow emitted from oneof the two battery modules 3, 3 disposed most forward or the emissionflows emitted from the two battery modules 3, 3 disposed most forwardare set the largest.

Furthermore, although in the foregoing example, the exhaust holes 7 a, 7a, 7 b, 7 b, and 7 b are provided, the number of exhaust holes formed inthe rear portion 7 of the housing case 2 is not limited to five but itsuffices that at least one exhaust hole is formed in the rear portion 7.

However, in order to improve the efficiency in emitting out of thehousing case 2 cooling air caused to flow through the upper side exhaustpath F1 and the lower side exhaust path F2, it is desirable that atleast one upper exhaust hole and at least one lower exhaust hole beprovided apart from each other in the vertical direction.

1. An onboard battery comprising: battery modules in each of which abattery cell is disposed; a housing case that houses the batterymodules; and an air intake duct configured to send cooling air into thebattery modules, wherein of the battery modules, at least two aredisposed apart from each other in a vertical direction and at least twoare disposed apart from each other in a front-rear direction, coolingair is taken into the battery modules from rear via the air intake duct,cooling air taken into the battery modules is emitted to an internalspace of the housing case, a rear portion of the housing case isprovided with at least one exhaust hole configured to let out thecooling air emitted from the battery modules to the internal space ofthe housing case, and of emission flows of the cooling air emitted fromthe battery modules to the internal space of the housing case, theemission flow of the cooling air emitted from at least one of thebattery modules which is disposed most forward is the largest.
 2. Theonboard battery according to claim 1, wherein one of the battery modulesis disposed most forward, two of the battery modules are disposed in anupper tier and a lower tier at a rear side of the battery moduledisposed most forward, and the battery module disposed most forward isdisposed in an intermediate tier in the vertical direction.
 3. Theonboard battery according to claim 2, wherein the battery modulescomprise five battery modules, and at the rear side of the two batterymodules disposed in the upper tier and the lower tier, two of thebattery modules are disposed in an upper tier and a lower tier.
 4. Theonboard battery according to claim 1, wherein the at least one exhausthole comprises a plurality of exhaust holes, and at least two of theexhaust holes are positioned apart from each other in the verticaldirection.
 5. The onboard battery according to claim 2, wherein the atleast one exhaust hole comprises a plurality of exhaust holes, and atleast two of the exhaust holes are positioned apart from each other inthe vertical direction.
 6. The onboard battery according to claim 3,wherein the at least one exhaust hole comprises a plurality of exhaustholes, and at least two of the exhaust holes are positioned apart fromeach other in the vertical direction.
 7. The onboard battery accordingto claim 1, wherein front surface portions of the battery modules areeach provided with a release hole configured to emit the cooling air tothe internal space of the housing case, one end portions of the airintake duct are provided as coupling portions coupled to rear endportions of the battery modules, and a rear surface of each of thecoupling portions is provided as a curved surface whose intermediateportion in the vertical direction is protruded rearward.
 8. The onboardbattery according to claim 2, wherein front surface portions of thebattery modules are each provided with a release hole configured to emitthe cooling air to the internal space of the housing case, one endportions of the air intake duct are provided as coupling portionscoupled to rear end portions of the battery modules, and a rear surfaceof each of the coupling portions is provided as a curved surface whoseintermediate portion in the vertical direction is protruded rearward. 9.The onboard battery according to claim 3, wherein front surface portionsof the battery modules are each provided with a release hole configuredto emit the cooling air to the internal space of the housing case, oneend portions of the air intake duct are provided as coupling portionscoupled to rear end portions of the battery modules, and a rear surfaceof each of the coupling portions is provided as a curved surface whoseintermediate portion in the vertical direction is protruded rearward.10. The onboard battery according to claim 4, wherein front surfaceportions of the battery modules are each provided with a release holeconfigured to emit the cooling air to the internal space of the housingcase, one end portions of the air intake duct are provided as couplingportions coupled to rear end portions of the battery modules, and a rearsurface of each of the coupling portions is provided as a curved surfacewhose intermediate portion in the vertical direction is protrudedrearward.
 11. The onboard battery according to claim 5, wherein frontsurface portions of the battery modules are each provided with a releasehole configured to emit the cooling air to the internal space of thehousing case, one end portions of the air intake duct are provided ascoupling portions coupled to rear end portions of the battery modules,and a rear surface of each of the coupling portions is provided as acurved surface whose intermediate portion in the vertical direction isprotruded rearward.
 12. The onboard battery according to claim 6,wherein front surface portions of the battery modules are each providedwith a release hole configured to emit the cooling air to the internalspace of the housing case, one end portions of the air intake duct areprovided as coupling portions coupled to rear end portions of thebattery modules, and a rear surface of each of the coupling portions isprovided as a curved surface whose intermediate portion in the verticaldirection is protruded rearward.
 13. The onboard battery according toclaim 1, wherein a front end portion of the housing case has, atlocations above and below the battery module disposed most forward,inclined portions that become farther apart from each other in thevertical direction toward rear.
 14. The onboard battery according toclaim 2, wherein a front end portion of the housing case has, atlocations above and below the battery module disposed most forward,inclined portions that become farther apart from each other in thevertical direction toward rear.
 15. The onboard battery according toclaim 3, wherein a front end portion of the housing case has, atlocations above and below the battery module disposed most forward,inclined portions that become farther apart from each other in thevertical direction toward rear.
 16. The onboard battery according toclaim 4, wherein a front end portion of the housing case has, atlocations above and below the battery module disposed most forward,inclined portions that become farther apart from each other in thevertical direction toward rear.
 17. The onboard battery according toclaim 5, wherein a front end portion of the housing case has, atlocations above and below the battery module disposed most forward,inclined portions that become farther apart from each other in thevertical direction toward rear.
 18. The onboard battery according toclaim 6, wherein a front end portion of the housing case has, atlocations above and below the battery module disposed most forward,inclined portions that become farther apart from each other in thevertical direction toward rear.